1. Field of the Invention
This invention relates to a dynamic projection adjusting method and a projection display device and; specifically to a projection adjusting method and a projection display device dynamically adjusting projection images according to brightness parameters of output images.
2. Description of the Prior Art
As consumer electronic devices have gradually entered the market, many projection display products for different consumer groups have been developed. The above-mentioned projection display products include digital light processing (DLP) projection devices, liquid crystal display (LCD) projection devices and liquid crystal on silicon (LCOS) projection devices, wherein the DLP projection devices have the advantages of high brightness, accurate color tone, fast response time, low screen noise, and small size. Therefore, the DLP projection devices have become one of the most popular new generation projection systems.
As far as the commonly known DLP (digital light processing) projection devices on the market are concerned, the main structure is based on micro electro mechanical systems (MEMS) and uses digital micromirror devices (DMD). The DLP projection device includes a light source, a color wheel module, a light pipe, a lens set for light separating and coupling, a digital micromirror device and an imaging lens. Please refer to FIG. 1, a schematic view illustrating a conventional projection display device is provided. The projection display device 1 in FIG. 1 is a DLP projection device, wherein the light generated by the light source 10 will pass through the color wheel 12 which has light filtering regions for different colors. For different projection display products, the light passing through the color wheel will then pass through the light pipe and the lens set for light separating and coupling processes. Finally, the light will be concentrated on the digital micromirror device 14 (DMD), wherein driving electrodes will be used to control the tilt angles and the deflection time of the micromirrors on the DMD 14 to switch the reflection direction of the light so that the light is projected by the imaging lens 16 onto a screen to form images. Compared with projection devices based on other principles, the DLP projection devices have the advantages of high brightness, accurate color tone, fast response time, low screen noise and small size.
As mentioned above, in conventional DLP projection devices, the light generated by the light source 10 is separated by the color wheel. Conventional DLP projection devices can be classified into different categories according to different applications. For instance, traditional color wheel with red, green and blue color regions are used when color lifelikeness and saturation are to be enhanced. The color wheel with white, green, blue and red color regions are used when high image brightness is to be enhanced. Recently, a color wheel having pure color regions of green, blue and red plus mixed colors of cyan (green plus blue), yellow (red plus green) and white has been developed.
As for the user experience of the projection device, the current requirement requires projection devices to perform excellent performances in various attributes, such as projection size, brightness, lumen, contrast ratio and color saturation to meet the consumers' expectation.
According to the current industry standard, the contrast of the projection device is usually defined by the ratio between the flux-white and flux-black.
In order to improve the contrast of the image, conventional projection devices usually adjust the power of the light source, such as the wattage of light bulbs. For instance, the contrast of the images under the normal display mode can be defined by:Contrast=Flux-White (Full Power)/Flux-Black (Full Power)
Under the enhanced contrast mode, the power of the light source is decreased to adjust the brightness contrast of overall display images and defined by:Adjusted Contrast=Flux-White (Full Power)/Flux-Black (Full power*Adjustment Ratio)
In this way, the contrast is increased in direct proportional to the reduction of the power of the light source. However, conventional contrast increasing technology requires frequently switching of the total power of the light source which greatly shortens the light source's life and creates additional maintenance costs for user as well as adversary influences on the stability the projection device's stability.
In order to solve the above-mentioned problems, a dynamic projection adjusting method and a projection display device for solving the above-mentioned problems and improving the contrast of the display images are required.